Saturday, February 25, 2012

Staking the vampire pterosaur: Jeholopterus was NOT a vampire

It's a common misconception that staking the heart of a Stokerian vampire will do it in for good. In actuality, the characters of Bram Stoker's Dracula (above) only considered the undead truly out of action once they were staked through the heart (which only imobilised them, see, not killing them), decapitated, had their mouths stuffed with garlic flowers and the access to their tombs lined with holy masonry. This may seem like overkill, but, for the vampire mythos Stoker created, it is the only way to keep the blaggards down. In the last week, it's emerged that that palaeontological vampires need a similar heavy duty approach to ensure that they too don't continue to rise from the grave.

Enter, stage left, the hypothesis that the anuroganthid Jeholopterus was a Mesozoic vampire bat equivalent (image, above, from my upcoming book, shows the anuroganthid Anurognathus with a more accurate Insect Hawking Cookie Monster of Doom appearance, not a vampire). Proposed by David Peters in an abstract for the SVP annual conference of 2003, cited evidence for this idea stems from large caniform teeth inferred on the Jeholopterus holotype using DP's infamous digital photo interpretation (for anyone unfamilar with DP's work, you can see the most recent incarnation of it here). It is well known that palaeontologists have almost never seen eye to eye with Peters' interpretations of fossils or methods of analysing them, and a small body of literature exists that directly refutes his work (e.g. Bennett 2005; Hone et al. 2009) . Many other papers also disagree with his methods or conclusions. DP acknowledges his 'heretical' views and, indeed, has even named his blog after them: The Pterosaur Heresies. Our very own Pterosaur.Net even gets a good kicking at various points at TPH, but that's OK: we have our opinions (which we consider to be well supported and credible), and Dave has his (which we consider to be very poorly supported). I think we have to live with the fact that we're not going to agree with everyone in science, and, frustrating though this can be at times, we're much better off making sure our own work is as watertight as possible than constantly bickering with others.

The vampire Jeholopterus made a brief splash back in 2003, but was widely condemned by the entire pterosaur community. To many, this simply proved - again - that SVP perhaps needed to pay closer attention to the work they were allowing into their conference, but that was that. No peer reviewed paper on the vampire hypothesis followed, and no independent confirmation that Jeholopterus or other anurognathids were sanguivorous has been proposed. Instead, the long-held view that anurognathids were ace aerial insect hawkers has prevailed (e.g. Bennett 2007; Habib 2011 [a follow up publication to which is in the works. I'm lucky enough to have been invited in on the authorship and can promise that some of the stuff in it should blow your little socks off]). The vampire pterosaur idea, it seemed, was dead, the only remnants being the abstract, a few media stories, and the Jeholopterus page at DP's website. This week, however, the vampire Jeholopterus meme has risen from the grave, being portrayed in a half-credible light in this article and picked up elsewhere online. Several people, including myself, were a bit miffed at this, and, in full on SIWOTI mode, left comments on these articles. The original article seems to be picking comments that agree with the tone of the article as their 'featured' comments, hiding perhaps more informed opinions in other pages of the article. Hence, seeing as most people won't easily find these remarks, I thought best to regurgitate mine here. In short, I want to provide a one-stop shop for clarity on the vampire pterosaur hypothesis:

The idea was not peer reviewed, and it's publication in a collection of conference abstracts is not of comparable standing to other hypotheses of anurognathid palaeoecology

There was never any 'debate' amongst pterosaur workers on this idea: it was never considered credible by qualified researchers in the first instance, and rejected outright from the start.

There is no evidence that Jeholopterus, or any other pterosaur, was a vampire

There is no 'David Peters vs. Goliath' story here. DP's work is considered with the same scrutiny, not more or less, than any other piece of science. His ideas are rejected by other palaeontologists (amateur and professional alike, the only difference between many of whom is that some are paid to study fossils) because they have not stood up to this scrutiny.

Any claims to the contrary suggest very lazy journalism, I'm afraid, so shame on those who have given this idea even a whiff of credibility. With that, I'll hand you over to my rambly self of yesterday, when I commented on the article that inspired this post. Said article may make for required reading before you continue.

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This story has been told rather incorrectly. DP's 'publication' in 'the peer-reviewed Journal of Vertebrate Paleontology' was NOT peer reviewed: it was a short abstract for the SVP 2003 annual conference. I am confident as a 'professional' pterosaur worker myself that this paper would not have made it into any scientific journal, and it was rightly condemned by the pterosaur community as soon as it was made public. Along with the Bennett article mentioned here, a body of literature exists demonstrating that most, if not all, of David Peter's methods of reconstruction and image interpretation are flawed. The extraneous features he reconstructs for fossil animals (which have included, at one time or another, fantastic frills, sails, additional bones and teeth, long tails on short-tailed taxa, hatchlings clinging to their parent's body and others) have never been found on fossil specimens despite CT scanning, UV investigation and other analytical methods. The vast majority of DP's ideas are not corroborated by any studies except his own. In polite terms, DP's ideas are considered 'fringe' at best by palaeontologists, and very much the view of one individual. (animated vampire Jeholopterus feeding strategy, below)

I find it worrying that you wrote your article without uncovering or featuring these details. Likewise, the fact that you give the vampire Jeholopterus idea some credence with statements like 'what spurred the great debate' and 'without a living Jeholopterus to observe, we really cannot be sure of its unique attributes': there was never any debate, and the latter suggests a critical misunderstanding of scientific practise. Palaeontologists work, like all other sciences, by testing hypotheses: we are confident that Jeholopterus was not a vampire bat-like animal because it fails tests we can put against this idea. Does it bear large teeth for piercing flesh? No. None have ever been found on any actual specimen: the fact they have been found on someone's computer screen means nothing if they cannot be seen by some means on the actual fossil. DP probably picked up compression artefacts in the jpeg or cracks, shadows and prep marks in the matrix on the slab. Did Jeholopterus have a strong bite? Probably not, as the bones of the jaw are mechanically weak and slender, and ill-suited to anchoring strong muscles. Are there any alternative means it could use to pursue a vampire lifestyle? None that we can ascertain. Is there a more plausible hypothesis for the lifestyle of Jeholopterus? Yes: aerial insectivory, a lifestyle that decades of _actual_ peer-reviewed studies into anurognathid (the group that Jeholopterus belongs to) anatomy and biomechanics support without exception.

Finally, the portrayal of DP as a maverick, lone amateur 'informing' the body of professional palaeontologists is unfair. A great number of so-called 'amateur' palaeontologists produce work of the highest credibility without a whiff of controversy. Like DP, they work alone and draw their own conclusions, but find that their ideas are similar to those lucky enough to be paid to research palaeontological subjects. There is no conspiracy about preservation of dogmatic ideas or rejection of outsiders: the internet teems with blogs and forums where paid palaeontologists and 'amateuers' meet to discuss ideas at the highest level. I'm afraid to say I find this article very ill-informed and misleading, and hope this comment adds some balance to this page.

14 comments:

Interesting stuff, Mark and anything that gets a sneak peak at your pterosaur art can't be all bad. :-)

Due to an earlier interest in fractals, I've done a lot of fiddling with bitmap graphics over the years and was incredulous that anyone would think it appropriate to be digging into jpgs thinking to find things people who've seen the fossils missed without what they find being artifacts. Incredulous.

BTW, you're too modest, but I thought I should add a comment at i09 touting Dave Unwin's book and your site and upcoming book.

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As someone (an undergraduate admittedly) who has spent a lot of time looking at vampire bat dentition and skulls this idea is...fanciful to say the least. Even if you take the interpretation of large front teeth as true, puncturing with two large teeth is pretty inconsistent with how big sanguivores do business as far as I know (slicing seems to be the main method). A fun discussion nonetheless, and as Mike said above any hints on the upcoming book is good.

Mark,I see denial here and rejection, but no competitive candidate insitu interpretation of the Jeholopterus skull in detail comparable to what I offered in 2003 and offer still on my website. And it's been nine years since 2003. It would be more scientific for someone to provide a new interpretation of the Jeholopterus skull elements so we can compare one to one and come to an agreement. Simply decrying, denouncing and repudiating the best effort to date doesn't help us get closer to the truth. It makes everyone on that side of the fence look like their into denial.

I don't shrink from pointing out errors with evidence. Neither should you.

All the elements are there in Jeholopterus, simply trace them out and reconstruct them. Let's see what you come up with. Don't forget there's a large manual ungual on top of the skull that others overlooked.

I see your preferred illustration follows the Bennett model with a giant eyeball in the front half of the skull, a tiny slitlike antorbital fenestra and a wide parietal broadly separating the upper temporal fenestrae. The Bennett interpretation of the flathead anurognathid has so many basic autapomorphic errors that it is a monster, unlike any other known pterosaur. I'm surprised that you bought into it.

All of my many tracings and reconstructions of anurognathids follow basic pterosaur anatomy with small eyes in the back half of the skull and narrow parietals. All of my tracings find symmetrically identical left and right bones, which Bennett was unable to do, despite a dorsal exposure in the flathead anurognathid. His large so-called sclerotic ring was preserved edge-on, which never happens in other specimens. That's one maxilla and those divisions represent crushed bone around tooth roots. The real sclerotic rings, both of them, are visible near the back of the skull as small circles. All these are presented at reptileevolution.com

I present evidence that passes many tests including symmetry, fit within a reconstruction and phylogenetic similarity to sister taxa. I hope someone who disagrees with my reconstructions can do the same.

And please remind your readers that the Hone, Sullivan and Bennett (2009) paper questioning the concept of parallel interphalangeal lines several times agreed that lines could be drawn, never provided a five- or four-digit animal without such lines and that a rebuttal paper answered all of their misconceptions.

I don't think anyone has a problem with anurognathid skulls being very usual. Most parts of anurognathid anatomy are unusual in one way or another. Their skulls have always been hard to interpret, but the majority of pterosaur workers are happy that they had very wide, short and skulls with very large orbits. From what I can see, the Jeholopterus skull doesn't seem dissimilar to that of the better-preserved juvenile Anurognathus described by Bennett, but it's very hard to make out the majority of the bones in the former. The braincase and right side of the skull, in particular, are compressed into a virtually continuous mass, and I would be cautious about identifying any of the bones within it. Wang et al. (2002) - the chaps who described the actual specimen, not photographs - were equally hesitant. From what I can see, you have vastly overinterpreted what is discernible in the Jeholopterus holotype skull: I cannot see the features you outline in my photos of the specimen. By contrast, I can see exactly what Bennett interprets in the little Anuro. in my own photos of the same specimen, and agree with his interpterations.

Also, I'm sure you don't need reminding that conference abstracts are not considered credible publications in the way that peer-reviewed papers are. Many editors do not even allow abstracts to be cited in technical papers for this reason. This is probably why no-one has 'officially' rebutted your work: it has not yet been demonstrated as a hypothesis worth serious consideration in peer-reviewed literature. Indeed, the catalyst for this post was my annoyance at journalism that did not appreciate this distinction, not so much the idea itself.

It's so interesting that when Bennett (2007) came up with that bizarre, autapomorphic monstrosity that everyone glommed on to it, but when I produced a much more conservative reconstruction, with all parts identified and symmetrical - and plesiomorphic - the experts chose the monster.

You mentioned "virtually continuous mass" in the chaos of skull bones and that is exactly what I saw before picking out first one element then another using Photoshop, until all pixels were accounted for. Then, by copying and pasting to make sure I didn't cheat, the reconstruction was created and every part fit. What more could you want? Yes, it's difficult. Jeholopterus took a month.

Then I duplicated the method with the other anurognathids and achieved the same sort of results.

Simply looking doesn't work with these chaotic roadkills. You have to digitally remove the layers of elements one at a time to achieve any sort of success and understanding.

You might ask yourself, what is the closest known sister taxon to the anurognathidae? Peteinosaurus and MCSNB 8950 don't have a skull, unfortunately. You have to go back to Dimorphodon and Preondactylus, and they both have a large antorbital fenestra and small eyes in the back of the skull like other pterosaurs. Where is the giant orbit in Dendrorhynchoides or the CAGS specimen attributed to Jeholopterus? Should be visible if similar to Bennett's reconstruction, but nothing of the sort will ever be found. I found the sclerotic rings of both, and they are small and in the back of the skull.

So, ALL the tests that can possibly be applied to the Bennett anurognathid have to be applied and found to be continuous across a phylogenetic gamut of anurognathids. When that happens, let me know...

I'm sure you can predict my response: with the exception of the juvenile Anurognathus, all anurognathid skulls are incompletely preserved and and badly crushed. They could not reveal the same information as seen in Bennett's reconstruction because of this.

"ALL the tests that can possibly be applied to the Bennett anurognathid have to be applied..."

So how do you explain that others can see the bones and features outlined in Bennett's Anuro. reconstruction in the actual fossil, but they cannot do the same for yours?

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I don't know why David Peters even considered his renditions of pterosaurs a scientific possibility. I mean, take his restoration Pteranodon for example: all those frilly structures on its body would most certainly inhibit its ability to fly. Flying animals today have to be areodynamic and lack all those frilly features. Pteranodon, being more at home on the air than on the ground, would have needed to be aerodynamic too.

A point here: why would vampire bay analogs need the flappy wings that these muppets have? Or the excessive g- loading capabilities that would seem totally unnecessary? Vampire bats are strong, but I'm pretty sure they're considerably weaker than insect- hawking bats. The strong terrestrial capabilities are mysterious, suggesting that they may have perched atop a branch or something waiting for a large bug to fly by, but on the other hand, strong terrestriality is a common feature in smaller pterosaurs, and their land locomotion might not have been used in hunting at all.

A point here: why would vampire bay analogs need the flappy wings that these muppets have? Or the excessive g- loading capabilities that would seem totally unnecessary? Vampire bats are strong, but I'm pretty sure they're considerably weaker than insect- hawking bats. The strong terrestrial capabilities are mysterious, suggesting that they may have perched atop a branch or something waiting for a large bug to fly by, but on the other hand, strong terrestriality is a common feature in smaller pterosaurs, and their land locomotion might not have been used in hunting at all.